Onceapilot
If you continue working after April 2016, your state pension will increase by over £4.50 per week for every extra year that you paid NI, since contracting out ceased in 2006. So if you work for another 7 years+ you will have made up the difference and will get the full state pension of £159. That said, you make good points about potential rule changes versus additional voluntary NI contributions. However, you have to plan on current rules - note that state pension changes are not supposed to occur within 10 years of retirement date ("trust me I'm a politician"!!).
As others have said, public sector pensioners have a huge advantage over most private sector money purchase scheme recipients, so I would suck it up and enjoy the index linked pension!
F.O.D